FIG. 1 depicts wideband digital radio receiver 100 in the prior art, which may also be known as a "block" or "software" radio. Wideband digital radio receivers are increasingly common and are characterized by the fact that they digitize an incoming multi-carrier signal and separate the carrier signals digitally, in contrast to more conventional receivers that separate the carrier signals using analog bandpass filters and then digitize each carrier signal individually.
Wideband digital radio receiver 100 typically comprises antenna 101, RF front end 103, analog-to-digital converter 105 and channelizer 107. Antenna 101 receives a multi-carrier RF signal and converts it into an electrical signal for RF front end 103, in well-known fashion. RF front end 103 amplifies the multi-carrier signal, typically using a low-noise amplifier, and downconverts the multi-carrier signal to either baseband or a suitable intermediate frequency, also in well-known fashion. Analog-to-digital converter 105 digitizes the multi-carrier signal, in well-known fashion, and channelizer 107 isolates and demodulates each carrier signal of interest using digital signal processing techniques, in well-known fashion.
FIG. 2 depicts a graph of the signal strength for each of twelve frequency-disparate carrier signals in an illustrative multi-carrier signal. When the signal strength of one or more of the carrier signals is great, the danger arises that the strong carrier signals could saturate analog-to-digital converter 105. Because analog-to-digital converter 105 has a non-linear frequency response, the potential exists that intermodulation products or "intermods" could be introduced into the digitized multi-carrier signal. Intermodulation products are clearly disadvantageous because they can attenuate or distort other carrier signals in the digitized multi-carrier signal.
Therefore, the need exists for a technique that prevents strong signals in a multi-carrier signal from saturating a device with a non-linear frequency response.